DESCRIPTION (Taken from the application): Hip fracture is one of the most severe implication of Osteoporosis, a disease affecting millions of elderly people world-wide. The clinically established method to predict a person's hip fracture risk, bone densitometry, cannot separately measure the status of trabecular and cortical bone but only reports overall bone density. There is evidence that both compartments individually contribute to bone strength but are differently affected by aging or osteoporotic changes and therapeutic regimens. This research effort will approach the following questions: Can the density and the thickness of cortical bone in the proximal femur be measured accurately with volumetric Quantitative Computed Tomography (vQCT)? Does the knowledge of these parameters aid in predicting mechanical integrity in addition to standard bone densitometry? To what extent is the technique applicable in vivo? To assess the accuracy of vQCT, a comparison to Micro-CT is planned. Micro-CT is a Computed Tomography technique on microscopic level (the spatial resolution is 25 mm for the instrument being used) and has recently been extended to scan whole proximal femora. It can therefore be used as a gold standard to evaluate vQCT. Out of a total of 25 excised cadaveric proximal femora from elderly women who did not have diseases known to affect bone, 5 will be scanned with vQCT and Micro-CT. The analysis tools, which will comprise segmentation of the cortical wall and local measurement of cortical bone mineral density and thickness, will be applied to both data sets. The other 20 specimens will be subjected to vQCT, standard bone densitometry and mechanical testing. During the latter, bone elasticity and ultimate failure load will be recorded. The gathered data will allow to estimate the relative contribution of the cortical thickness and density to mechanical integrity and to locate the most sensitive regions of the cortex. The question of whether a vQCT scan of cortical bone can add information to standard bone densitometry can also be answered. The third part of the study will focus on clinical feasibility of vQCT of cortical bone. Its specific aim is reducing the radiation exposure by limiting the CT scan volume and decreasing the amount of radiation used. By analyzing the impact of the consequential increase of image noise and loss of spatial resolution on the measurability of cortical density and thickness optimal CT imaging parameters will be derived.